Drive arrangement for oscillating the needle cylinder of a circular knitting machine



Feb. 18, 1969 HQ 3,427,830

DRIVE ARRANGEMENT FOR OSCILLATING THE NEEDLE CYLINDER OF A CIRCULAR KNITTING MACHINE Filed May 5, 1967 I r C E A Q I Q p 52y. 2 a S i R 0 w 5, z I. l

A 0 t A, E B 0 INVENTOR. fa z/-e/ ZA/ff United States Patent Claims ABSTRACT OF THE DISCLOSURE In a circular knitting machine whose needle cylinder is oscillated about its axis by an electric motor connected to the cylinder by a crank transmission, an induction coupling is interposed between the motor and the crank transmission, and the electric power which normally keeps the coupling engaged is reduced by a regu' later when the output voltage of an electric tachometer coupled to the cylinder exceeds a certain value.

Background 0 the invention This invention relates to circular knitting machines and particularly to a drive arrangement for oscillating the needle cylinder of the machine about its axis, for ex ample, during the knitting of the heel on a hosiery machine.

It is known to connect the continuously rotating output shaft of a drive motor with the cylinder by means of a crank transmission which converts the continuous rotation of the output shaft into angular oscillating movement of the cylinder. The angular velocity of the cylinder is an approximately sinusoidal function of the angular position of the cylinder in such an arrangement.

The rate of angular movement of the cylinder is limited by design considerations such as the strength of the materials employed, the effect of centrifugal force on machine elements which move with the cylinder, and the like. Each circular knitting machine is inherently limited to a critical maximum velocity of angular cylinder movement. Because of the approximately sinusoidal relationship between cylinder velocity and cylinder position in the conventional crank arrangement, the inherent maximum velocity of the cylinder restricts the rate of cylinder acceleration and deceleration, and sets a lower limit to the length of each cycle of oscillating movement, thereby limiting the production rate of the knitting machine.

It has been attempted to overcome the limitations of the known drive arrangement by interposing cam elements between the crank transmission and the needle cylinder which convert the approximately sinusoidal relationship between cylinder velocity and cylinder position into a relationship more closely represented by a square wave, but these modified drive arrangements are relatively complex and require careful and laborious maintenance.

Summary 0 the invention It has now been found that rapid cylinder acceleration and deceleration virtually independent of the permissible maximum rate of angular cylinder displacement can be achieved if the input portion of a motion transmitting device is connected to the motor, the output portion of the device is-connected to the transmission, such as a crank transmission, which converts the continuous rotation of the motor shaft into oscillating movement of the cylinder, and the ratio of the rotary speed of the output portion to the rotary speed of the input portion is reduced by a control device connected to the cylinder and to the motion transmitting device in response to the rate of angular cylinder movement when this rate exceeds a predetermined limit close to the permissible maximum rate.

Suitable motion transmitting means include an electrically operated coupling whose operating power is controlled in response to the cylinder velocity.

The necessary signal may be derived from the angular movement of the cylinder in any desired manner. An elec- V tric tachometer connected to the needle cylinder for joint movement produces an output voltage proportional to the cylinder velocity, and has been found a convenient source of a control signal for the electrically operated coupling.

Among the advantages of this arrangement are its simplicity and corresponding freedom from maintenance difficulties, and the fact that only the motor and the input portion of the motion transmitting device rotate at constant high velocity at all times whereas the rate of movement of all other drive elements, particularly of reciprocating drive elements, is limited to a relatively low value.

Other features and the attendant advantages of this invention will be readily appreciated from the following description of a preferred embodiment when considered in conjunction with the attached drawing.

Brief description of the drawing In the drawing:

FIG. 1 shows a circular knitting machine equipped with the drive arrangement of the invention in fragmentary elevational section; and

FIG. 2 graphically illustrates relationships of certain operating variables in the machine of FIG. 1.

Description of the preferred embodiment Referring now to the drawing in detail, and initially to FIG. 1, there is seen as much of a circular knitting machine as is needed for an understanding of the invention, the non-illustrated portions of the machine being conventional and not in themselves relevant to this invention.

The electric constant-speed motor 1 of the knitting machine drives a pulley 3 through an induction coupling 2 whose input portion is mounted on the output shaft of the motor. The coupling is known in itself and not illustrated in detail. Torque is transmitted from the motor 1 to the pulley 3 in the coupling 2 by the interaction of the magnetic field produced by magnetic poles on one rotating member of the coupling and currents induced in the other rotating member.

A belt 3' connects the pulley 3 with a pulley 4 fixedly mounted on a shaft 5 which is journaled in the stationary frame 30 of the knitting machine. A gear 6 on the shaft 5 meshes with a gear 13 which is freely rotatable, but axially secured on a shaft 15.

The gear 6 also meshes with a gear 7 journaled in the machine frame 30 and provided with an eccentric pin 8. A link 9 hingedly connects the pin 8 with an axial pin 10 on a gear segment 11 which is pivotally mounted on the frame 30. The segment 11 meshes with another gear 14 which is rotatable, but axially secured on the afore mentioned shaft 15. The gears 13, 14 are elements of a shifting mechanism" which includes an axially movable coupling member 12 secured against rotation on the shaft 15, but axially shiftaible thereon in the directions of the arrows S and S between positions of driving engagement with the gears 13, 14 in a known manner not illustrated in detail.

A bevel gear 16 on the shaft 15 meshes with a bevel gear 17 on the needle cylinder '18 which turns about a vertical axis on the frame 30. When the coupling member 12 is engaged with the gear 13, the cylinder 18 is rotated continuously in one direction. When the coupling member 12 engages the gear 14, the cylinder 18 performs an angular oscillating movement about its axis.

A gear 19 on the cylinder 18 meshes with a smaller gear 20 on the input shaft of an electric tachometer 21 whose output terminals 22 are connected by conductors 23 with the input terminals 25 of a differential voltage regulation 24 of a known type which includes a source of a reference voltage, and whose output voltage is constant unless the input voltage supplied by the tachometer 21 exceeds the reference voltage which may be adjusted in the regulator 24. When the tachometer output voltage is higher than the limiting value, the output voltage of the regulator 24 drops.

The output terminals of the regulator 24 are connected with the input terminals 26 of the coupling 2 by conductors 27. The motor 1 is equipped With conventional controls, partly indicated at 28.

FIG. 2 diagrammatically illustrates the relationship of the angular velocity of the cylinder 18 and of the output voltage of the regulator 24 to the angular position of the cylinder 18 during operation of the knitting machine of FIG. 1.

In the absence of the feedback loop constituted mainly by the tachometer 21, the regulator 24, and the coupling 2, the angular speed of the cylinder 18 would be a sinusoidal function of its angular position. The curve P partly shown in broken lines in FIG. 2 illustrates the re lationship of the angular velocity of the cylinder 18 to the angular position of the cylinder during each revolution of the gear 7 when the feedback loop is inoperative and the coupling 2 is continuously engaged, while the coupling member 12 rotates with the gear 14. The coupling 2 is held in engagement by the normal power output A of the regulator 24.

When the feedback loop is operative as shown in the drawing, the output voltage of the tachometer 21 cannot exceed the limit set in the regulator 24 at the peak velocity of the cylinder 18, and the output of the regulator 24 is gradually decreased to a value A insufficient to keep the coupling 2 in full engagement, as indicated by the curve Q in FIG. 2. The resulting slippage in the coupling 2 reduces the peak speed of the oscillating cylinder movement to a level R in either direction, and the actual relationship between the angular velocity and the angular position of the cylinder 18 is shown in FIG. 2 by the fully drawn curve P.

It is evident from FIG. 2 that the acceleration rate and deceleration rate of the cylinder are much higher than could be obtained in a purely sinusoidal relationship of velocity and displacement at the same peak velocity, and that the cycle of oscillating movement is shortened at equal angular displacemen The productivity of the knitting machine during oscillating needle cylinder movement is thus increased by the feedback arrangement of the invention.

While the invention has been described with specific reference to a crank transmission for converting continuous rotary motion into oscillating rotary motion, it will be appreciated that the invention is applicable to transmissions in which an eccentric, a cam, or a system of levers is employed for the same purpose.

Similar modifications are possible in the feed back loop which varies the ratio between the rotary speed of the motor shaft and the input speed of the transmission. While a tachometer has obvious advantages, the use of a potentiometer operated by a cam connected to the cylinder is specifically contemplate-d, and other devices for deriving an electrical velocity signal from the cylinder will readily suggest themselves.

The regulator 24 may be replaced by analogous devices which respond only to velocity signals exceeding an adjustable threshold value, and which reduce the operating power of the coupling 2 in response to the magnitude of a signal.

While an induction coupling has been illustrated and described, and is being preferred, an electrically operated magnetic clutch is also effective. Ultimately, a friction clutch operated by means of a solenoid is within the scope of this invention, though limited in its application.

It should be understood, therefore, that the foregoing disclosure relates only to a preferred embodiment of this invention, and that it is intended to cover all changes and modifications of the example of the invention chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. In a knitting machine having a needle cylinder rotatable about an axis, a drive motor having an output shaft, and a transmission interposed between the motor and the cylinder for converting continuous rotation of the output shaft into angular oscillating movement of the cylinder, the improvement comprising:

(a) motion transmitting means having an input portion drivingly connected to said output shaft and an output portion drivingly connected to said transmission; and

(b) control means connected to said cylinder and to said motion transmitting means for reducing the ratio of the rotary speed of said output portion to the rotary speed of said input portion in response to the rate of angular movement of said cylinder when said rate exceeds a predetermined limit.

2. In a knitting machine as set forth in claim 1, said motion transmitting means including an electrically operated coupling, and said control means including means for controlling the operating power for said coupling.

3. In a knitting machine as set forth in claim 2, said control means including an electric tachometer connected to said needle cylinder for joint movement.

4. In a knitting machine as set forth in claim 1, said transmission including a crank mechanism and said motor being a constant-speed motor.

5. In a knitting machine as set forth in claim 4, said motion transmitting means including an induction coupling, and said control means including an electric tachometer connected to said needle cylinder for joint movement, and means for energizing said coupling in response to the output of said tachometer.

References Cited WILLIAM CARTER REYNOLDS, Primary Examiner. 

